Effect of heat treatment conditions on the internal and external oxidation processes in non-oriented electrical steels

In order to obtain desired magnetic properties, the samples of non-oriented electrical steels were subjected to various annealing treatments in gas mixtures. In the case of fully processed electrical steels the annealing performed by manufacturer to reduce the carbon content and to develop the grain growth with favourable texture. In the case of the semi-processed electrical steels an annealing treatment by the customer is needed to relieve the residual stress and to develop the grain growth. The carbon contents have to be low to prevent ageing process. However, the effect of this treatment is known to be very sensitive to operating conditions, such as temperature, time, type of atmosphere, etc.